Police in Cambridge, Mass., are being criticized for the arrest of a black Harvard student in which the 21-year-old was pinned down and struck in the stomach repeatedly by an officer.

The student, who police identified as Selorm Ohene, was arrested around 10 p.m. Friday and charged with disorderly conduct, indecent exposure, resisting arrest and assault after police found him nude in the middle of a main street “acting completely irrational.” The man had been the subject of at least seven emergency calls, including one from a woman who said he had thrown his clothes at her.

Police said a woman they believed to be an acquaintance of Ohene told them that he had taken drugs that evening. Video taken by a bystander and released by the police shows the man being confronted by officers on a concrete median in the middle of a busy street, before he is dropped to the ground. One officer strikes him multiple times as he is down. A police report later said that Ohene was punched five times.

The use of police force has caused an outcry in the community around Harvard.

The university’s president, Drew Faust, called it “profoundly disturbing” in a letter on Monday.

“A Harvard student was in obvious distress, and we need to understand how that came to be and whether we could have interceded earlier and more effectively,” Faust wrote. “We have been witness to the use of force against a member of our community, which, regardless of circumstances, is upsetting and compels the search for a deeper understanding.”

The university’s black law student association said that a number of its members witnessed what it called a “brutal instance of police violence,” saying in a statement that the student screamed for help as he was punched in the torso. The statement, which was signed by more than a dozen other student groups, said that “a pool of blood” was left on the pavement by the struggle. An image published by NBC shows blood in the street where the arrest happened.

The police have defended their response, which is under an internal investigation, though the officers - three from the Cambridge Police Department and one from Transit Police - have not been removed from duty. One is still receiving treatment for unspecified injuries suffered during the arrest, Cambridge Police Commissioner Branville Bard said.

“Numerous attempts were made by the officers to calm down the male, but they were met with opposition and hostility,” Bard told reporters at a news conference Monday. “After he was observed clenching his fists and moving towards officers, the decision was made to take the individual down.”

Bard, who is black, said officers are trained to use the least amount of force, along a “continuum” that begins with the officer’s arrival.

“It escalates to verbal commands. From there, to control holds to other less-than-lethal force being used, that could consist of punches, kicks, use of a baton or pepper spray,” he said.

Bard said officers had difficulty in getting one of Ohene’s arms from underneath his body to be able to handcuff him.

Ohene “was flailing, kicking, and the officers were doing everything within their power as they go up that force continuum to bring him into custody and compliance and control safely,” Bard said.

In an incident report released by the police, officer Steven Burke described the struggle that preceded the blows.

“We gave Ohene verbal commands to give us his hands which he did not,” Burke wrote. “Unable to pry Ohene’s hands from underneath his body, I delivered approximately 5 strikes with a closed fists to the area of his stomach.”

But the punches were ineffective, Burke wrote. Eventually other officers were able to pry Ohene’s arm from behind his back and handcuff his arms and shackle him at the ankles.

“It’s important to not gauge the officers’ actions within the context of an ideal construct and to actually gauge their actions within the context of a rapidly evolving situation,” Bard said. “To do so with 20-20 hindsight is unfair.”

Ohene was also charged with assault and battery on an ambulance personnel after police said he spat a mixture of saliva and blood at an EMT.